Method of destroying insects and microorganisms



Patented Aug. 29, 1939 UNITED STATES PATENT OFFICE Ivar Rennerfelt,Djursholm, Sweden No Drawing. Application September 1, 1934, Se-

rial No. 742,449. 1933 Claims.

The present invention has for its objects to provide an efiicient, cheapand harmless method for killing all kinds of vermin such as lice, fieas,moths, cockroaches, ants, etc., and microorganisms such as bacilli andbacteria in all kinds of localities such as living rooms, schoolrooms,assembly halls, hospitals, soldiers barracks, kitchens, magazines,passenger cars and other public vehicles, stables, etc.

The method consists principally in raising the temperature in the spaceto be treated tosuch a degree, that the vermin and microorganisms cannot survive the serious changes in their physiological conditions, whichtake place at a temperature between 40 and 45 C. as far as the insectsare concerned, whereas the microorganisms perish at a temperatureranging from 45 C. to about 65 C. and in a few cases somewhat higher.

In order to quickly raise the temperature sufficiently a powerful sourceof heat is temporarily introduced into the space and caused to produceheat at a controllable rate of speed and is placed at a nearly centralplace in the room. Preferg5 ably an oil burner or an appliance forburning a gaseous fuel may be used in the form of an easilytransportable stove capable of causing a complete combustion of thefuel. It is, naturally, possible to use also an electric heatingappliance in cases, where cheap and sufiicient electric power isavailable but ordinarily heavy oil such as is used in central heatingsystems will be found convenient, cheap and not liable to cause any firehazards.

The locality to be treated, especially if it is a living room, should bewell closed to prevent the vermin from escaping into adjacent rooms,which is likely to happen as practical trials with the new method haveindicated. The vermin quickly ap- 40 pear on the walls and furniture assoon as the temperature begins to rise above normal values and becomemore and more lively up to about 35 C., when the insects appear tobecome alarmed and try to find some means of escaping the unusualphysical conditions. Consequently the room under treatment must be wellclosed, which means that certain steps are required to keep the burnerin proper action without causing smoke and soot to spread in the room.

It is obvious that the amount of oxygen required to keep the burner inproper condition for a perfect combustion will gradually becomeexhausted, being partly replaced by carbon dioxide and steam, theatmosphere in the space becom- 55 ing composed of a hot mixture of saidgases and In Sweden September 4,

also a constant supply of fresh air for the maintenance of completecombustion. A sufficient stirring may be caused by providing acirculating fan close to the stream of hot combustion gases, which mayby this means become deviated in any desired direction, preferabydownwards in order to cause a more rapid heating, especially of thelower parts, for instance, the fioor and carpets, etc., on the floor. Ifsuch deviation of hot gases produced in the combustion zone is notprovided, it is obvious, that they will rise immediately to the ceilingcausing not only a very uneven distribution of the heat but also somedanger of very serious damage to the upper parts of the room.

The same is true in case the heat is being produced by means of anelectric heating appliance, which, thus, should be combined with meansfor efliciently circulating the heated air downwards to the floor andwall surfaces, avoiding overheating of the ceiling above the place,where the heat is being produced.

The circulation of the atmosphere is conveniently obtained by installingan electric motor for running the fan, which may be placed vertically orhorizontally or in an inclined position as demanded by the circumstancesin each case. To prevent overheating the windings of the motor should bedustproof and so enclosed that cool air may be caused to flow throughthe windings. The motor may be provided with a flexible hose connectedto the outside of the house or with adjacent rooms and may be caused todraw the required air by means of a circulating fan or by a specialsuction fan. It is, thus, possible to let the air required for coolingpurposes pass on into the zone of combustion, from where the surplus airmay escape together with the steam and CO2 in case all the oxygen is notconsumed. A convenient method of supplying the fresh air required is topass a hose or tube out through a narrow opening in a slightly openedwindow or door way, the rest of that opening being temporarily closedfor instance by a pad or the like. Any regular openingin the wallleading to a supply duct for fresh air, for instance a ventilation hole,may be used for the same purpose.

The flame of combustion is preferably com pletely enclosed by a heatresisting casing for confining the hot gases into a limited space andcausing them to rise upwards so that they become well mixed with apowerful downward fiow of air from the circulating fan above or on theside of the heating appliance such as the stove or an electricresistance.

Any kind of suitable burner may be employed operating with either low orhigh pressure, which may be supplied from a blower or a tank containingair under pressure. A convenient method of causing the oil to flow intothe burner is to use the air circulating fan for such purpose supplyinga suificient oil pressure in the container, in which the quantity of oilfor a certain heating operation is kept, thus, causing the oil to leavethe container, which may conveniently be located beneath the heatingstove. The entire apparatus may in this way consist of three principalparts, viz. the casing with the enclosed oil burner, an aircooled motorwith the air circulating fan above and the container for the oil supplybeneath the casing. The apparatus may be provided with automatic,preferably aircooled, relays and instruments for controlling thetemperature by acting upon the oil supply, the amount of air and otherfactors.

The oil for instance may be entirely shut off by the influence of apyro-stat on an automatic shutting off valve or it may be decreased orincreased according to the conditions in each case. The amount ofelectric resistance may in the same way be automatically controlled, incase an electric source of heat is being employed instead of a fuelburning appliance. if required by the circumstances it is possible toprovide the oil container with cooling means or with a heat insulatingcovering. This may be desirable when employing a temperature in theneighborhood of 100 C. for instance in cow stables and the like.

If desired the combustion gases when leaving the burner zone may becaused to pass into a system of tubes exposed to the air fiow from thecirculating fan. Such tube system may even be brought out into the openair for disposing of undesirable gases but normally no such gases norsoot will be produced in a well built and properly used apparatus forgasifying and oxidizing the liquid fuel, if such is used.

The oil or gas to be used as a fuel may be supplied alsofrom an outsidecontainer by means of a hose through a hole or a narrow opening in adoorway or the like but preferably the oil should be kept in a containerclose to the stove as described above. The appliance may, naturally, bemade in three or more separate parts but it is most convenient tocombine all the parts into one single piece of apparatus in order to beccnveniently transported and managed.

The method may be carried out in two different alternatives, viz. eitherby a slow gentle heating during a prolonged time of operation or by avery rapid rate of heating during only a few hours. The slow heating isto be preferred when it is desirable to prevent an undesirableoverheating of furniture having delicate polished surfaces. Rapidheating may be desirable in localities such as cow stables, barracks,warehouses, etc.

In many cases it may be possible to use the regular steam heat of anapartment for supplying a certain amount of the heat up to a certaintemperature, the extra heating required being employed for increasing itup to the desired limit. The method comprises, furthermore the use ofsmaller heating appliances adapted to be carried around by hand forinjecting hot air into crevices, narrow places, holes, etc., where thevermin may be present, especially down at the floor line around thewalls, inside of small closets and wardrobes, etc. Such appliances maybe equipped with a source of heating in the shape of an enclosed flame,which is deviated by a current of air from an electric motor fan. It ispossible also to inject water or steam into the locality in order toinfluence the conditions of the air by controlling the humidity asdesired. Certain gases, detrimental to the insects, may also be injectedtogether with the heated gases or separately.

For the sake of increasing the safety a container filled with a fireextinguishing matter, for instance CO2, may be provided near the heatingapparatus and caused to operate for instance by means of a lowtemperature fuse opening a valve, if the temperature exceeds apermissible limit,

To protect sensitive surfaces and objects heat insulating covers may beapplied if high temperatures would cause damage to such objects.

I claim:

A method of killing insects and microorganisms in a substantially closedspace which comprises introducing hot non-poisonous gases substantiallycomposed of a mixture of CO2, H20, and air, creating a blast of saidgases, initially and continually directing said gas downwardly while thegas is at its highest temperature, and causing circulation thereof untilthe entire space is substantially uniformly filled with said gas atlethal temperature.

2. A method of killing insects and microorganisms in a substantiallyclosed space as defined in claim 1 in which the hot non-poisonous gasesare generated within the closed space by the combustion therein of afluid fuel.

3. A method of killing insects and microorganisms in a substantiallyclosed space as defined in claim 1 in which the hot non-poisonous gasesare generated within the closed space by the combusion therein of afluid fuel with air delivered as such to the zone of combustion of saidfuel from outside said closed space.

4. A method of killing insects and microorganisms in a substantiallyclosed space which comprises generating hot non-poisonous gaseousproducts of combustion therein by burning a liqued fuel with airdelivered as such to the zone of combustion of said fuel from a pointoutside said space, creating a downwardly directed blast of theatmosphere within said space adjacent the zone of combustion of the fuelwhereby said blast mingles with the hot products of combustion and themixture flows first toward the bottom of said space impinging againstthe bottom thereof and then circulates within said space, and continuingsaid blast and the circulation of said mixture until the whole of saidspace is substantially uniformly heated to a temperature suflicient tokill said insects and microorganisms.

5. Method of killing insects and microorganisms in a substantiallyclosed space as defined in claim 4 in which said combustion zone issupplied with fuel from a body thereof maintained in said space and inwhich said body of liquid fuel is maintained at a temperature below thatattained in said closed space by heat exchange with the air delivered tothe combustion zone.

IVAR RENNERFELT.

